Invented by the Greeks in 400 B.C.,catapults were used in ancient and medieval times to hurl stones, spears, and other objects at fortifications.

The crossbow was invented in China but developed into a significant weapon in medieval Europe. With a mechanism for holding the drawn bow until it was ready to release, it propelled arrows with tremendous force as far as 350–400 yards. The crossbow allowed soldiers to fire from great distances and avoid close contact with the enemy. Swords, which had to be used at close range, were no match.

The discovery of gunpowder led to the development of cannons in the 1300s. Cannons could demolish castle walls and blast through wooden ships.

Machine guns allowed for rapid, continuous fire, thereby eliminating frequent reloading. The first was the Gatling gun, used in the American Civil War.

The tank, an armored combat vehicle equipped with a cannon and machine guns, replaced the use of rifles in war. It put an end to trench warfare, since tanks, with their caterpillar traction, could easily bulldoze over trenches. Tanks were first used at the end of World War I, and they emerged as a symbol of modern warfare.

Combat aircraft, both bombersand fighter planes, changed the nature of war during World War II. Air superiority became critical to victory. The British Spitfire, American Mustang, and German Messerschmitt were among the most famous fighter planes of the war.

Nuclear weapons,first developed in 1945, allow for massive destruction. Atom and hydrogen bombs are examples of nuclear weapons. Because these weapons are so perilous to human existence, treaties limit their development.

Smart bombs (or precision-guided munitions) are highly accurate bombs that are guided to their targets by computers. Smart bombs hit their targets much more frequently than dumb bombs (which are unguided) and cause both fewer casualties and less damage to civilian areas.